1. Field of the Invention
This invention relates to watercraft with an outboard drive, and more particularly to an improved tilt and trim system for an outboard drive.
2. Description of Related Art
In many types of marine propulsion systems such as outboard motors, there is provided a hydraulic cylinder assembly that is interposed between the outboard drive of the propulsion system and the watercraft transom. The hydraulic cylinder assembly provides a number of purposes. For instance, the hydraulic assembly is employed for tilting and trimming the outboard drive. The tilt movement is accomplished to tilt up the drive unit out of the water when it is not in use or for other purposes such as maintenance or inspection, etc. and tilt down the drive unit from the tilted up position. The trim movement is accomplished to trim up or down the drive unit for adjusting positions of the associated watercraft in response to speed thereof.
Obviously, in order to permit trimming when operating under power, the hydraulic cylinder assembly must provide large force. This can be easily accomplished by providing relatively large effective piston areas over which the hydraulic pressure operates. However, these types of mechanisms, although providing good hydraulic force for the trim operation, are very slow in the tilt up operation.
Therefore, it has been proposed to employ one trim fluid motor to provide the trim adjustment. This trim fluid motor has a relatively large diameter piston and, thus, has a relatively low stroke for a given fluid displacement In addition, a smaller bore, but longer stroke, tilt fluid motor is also coupled to the outboard drive for effecting the tilt up operation. Thus, high speed tilting can be accomplished without loss of power for the trim operation. However, the outboard drive only permits a small space between the outboard drive and the watercraft transom to employ fluid motors.
There have been proposed, therefore, telescopic or compound hydraulic cylinder assemblies wherein single external cylinders are provided. A tilt cylinder is slidably supported in an outer cylinder defining an internal cavity in which a tilt piston is movable. Basically, these assemblies operate by effecting hydraulic pressure actuation of both the trim and tilt cylinders simultaneously for a portion of the stroke during which trim movement is accomplished. The tilt cylinder is then held and the tilt piston, which has a smaller effective piston area, is operated for tilt up operation.
As is readily understood, a range for the trim movement exists below a range for the tilt movement. The drive unit moves from a fully trimmed down position to a fully trimmed up position within the trim range and then moves from the fully trimmed up position to a fully tilted up position within the tilt range. The drive unit moves back from the fully tilted up position to the fully trimmed down position by conversely tracing the moving up operation. These sequences must be strictly held for systematic operation of the hydraulic system. That is, in the moving up operation, the trim movement must precede and then the tilt movement follows. Meanwhile, in the moving down operation, the tilt movement must precede and then the trim movement follows. In order to prevent inverse operations from occurring, the hydraulic system usually employs specific mechanisms. A latching mechanism is provided, as one of the mechanisms, to hold the tilt cylinder in a fully trimmed up position during the tilt down movement.
Also, a piston rod which extends from the tilt piston supports the drive unit. The drive unit has a relatively heavy weight The piston rod and then the tilt piston, must receive the weight and shock, i.e., reaction force of the drive unit. Since the tilt cylinder slidably supports the tilt piston therein, ultimately the tilt cylinder needs a section for receiving the reaction force therein.
U.S. Pat. Nos. 5,718,613 and 5,746,055 disclose latching mechanisms and reaction force receiving members. However, they are provided separately with each other and hence constructions of the cylinder assemblies are somewhat complicated. More neat and simple arrangement, therefore, is desired. In addition, the reaction force is received by snap rings provided in these cylinder assemblies. Although the snap rings are generally sufficient to receive such force, it is desirable to receive them by a member which is more rigid than the snap ring in case of a relatively large force exerting upon the member.
It is, therefore, a principal object of the present invention to provide a telescopic hydraulic system that has a latching mechanism and a reaction force receiving section in more simple and neat fashion, and also a relatively large reaction force can be received more than enough.
The telescopic cylinder assembly of the hydraulic system is conventionally disposed off to the side from the axis of the bracket assembly because, for example, a relatively large electric motor that activates a fluid pump delivering working fluid is parallelly placed on the other side of the axis of the bracket assembly. However, this arrangement is not always suitable for every outboard motor due to concentration of stress. The cylinder assembly is desirably disposed on the axis of the bracket assembly or as near as possible. In this improved arrangement, however, space for a component such as an electric motor is quite limited. Particularly, if the telescopic cylinder has a lower portion thicker than an upper portion, this problem is serious.
It is, therefore, another object of the present invention to provide a cylinder assembly that can be disposed on the axis of the bracket assembly or as near as possible, even if its lower portion is thicker than the upper portion thereof.
Also, the hydraulic cylinder assembly needs a fluid conduit that is arranged to deliver the working fluid to the second internal cavity defined in the tilt cylinder. Since the fluid conduit is desired to be joined at the uppermost position of the tilt cylinder, conventionally this fluid conduit is disposed within the upper space. The upper space, therefore, is reduced by the conduit to a greater or less extent.
It is, therefore, a further object of the present invention to provide a telescopic hydraulic system that has no conduit within the upper space.